Acylating furan



Patented Feb. 8, i949 ACYLATIN G FURAN Howard D. Hal-tough, Pitman, N. J., and Alvin I. Kosak, Columbus, Ohio, assignors to Socony- Vacuum Gil Company, Incorporated, a corporation of New York p I No Drawing. Application June 20, 1946,

Serial No. 678,158

This invention relates to a process for the ac ylation of furans and, more particularly, is directed to a catalytic method for acylating furan and its derivatives in the presence of a small amount of a porous absorptive silica-hydrous metallic oxide;

. Acylation reactions are .well known in the art andconnote the union between acyl radicals and molecules of organic. compounds under conditions of temperature, pressure and time ordinarily referred to in the art as acylating conditions. The

compounds thus produced represent structurally V the substitution of the original acyl radical for a hydrogen ecule. i

As aflgeneral. rule, the temperature, pressure and time of reaction employed in acylation operations depend upon whether the acylation is effected in vthe absenceor presence of catalysts. The two methods are generally referred to as thermal and catalytic acylation, respectively. The majority of acylation processes fall under the latter category and it is a catalytic acylation process with which the present invention is concerned. i v

Y Acyl radicals may be furnished in acylation reactions by various materials commonly referred to as acylatingagents. Thus, the anhydrides of carboxylic acids and acyl halides have served as sources of the acyl radical. In particular, acetic anhydride and acetyl chloride have found wide application as acylating agents.

The acylation of furan and furan derivatives has previously been carried out employing one of the'above-mentioned acylating agents in the presence of various catalysts including stannic chloride, ferric chloride, aluminum chloride and titanium tetrachloride.

These catalysts, although applicable with considerable success in the acylation of aromatic hydrocarbons,- are only moderatelysuccessful where atom on the organic compound molfuran is involved. It has been postulated that thismay be accounted for by the fact that compounds such as aluminum chloride form addition complexes with the ether linkage in furan substantially decreasing the yield of desired product and requiring a considerable excess of aluminum chloride over the theoretical amount required for the acylation reaction. Thus, when -aluminum chloride is used as the condensing agent, the ratio of catalyst to acyl chloride is at least one and, in-the'case of acid anhydrides, at least two. hikewisg other catalysts of the Eriedel-Crafts type -mustbe used in molecular quantities with respect to ,the acylating agent being employed 14. Claims. (01.2604345) inthe acylation of furan. Moreovenin using the above catalysts, it has been necessary to con-i fine the acylation process to a batch operation.

It has now been discovered that acylated furans may be obtained in an efiicient manner by reacting the furan to be treated with an acylating agent in the presence of a porous absorptive silica'- hydrous metallic oxide catalyst. It has been found that by using said catalyst, the above-mentioned difiiculties encountered in the acylation of furans have largely been overcome. It would appear that the advantages obtained using a silica-hydrous metallic oxide catalyst can be attributed to the fact that relatively small .quantities of this material can be used as an effective catalyst in the acylation of furans. It has been found that silica-hydrous, metallic oxide composites efiect the acylation of furans without accompanying formation of complex addition prod: ucts formerly encountered in catalytic acylation processes. It has been found,'in accordance with this invention, that silica-hydrous metallic oxide composites employed in relatively small amounts in comparison to the quantity of furan or acylati'ng agent used efiect the acylation of furan and that such composites are readily reactivated, lending themslves to a continuous acylation operation. ,Thus, silica alumina, silica zirconia, silica-thoria, and like catalysts contemplated for use herein may, after employment in promoting the acylation reaction, be reactivated by conventional means. A continuous process of acylation employing suchcatalysts may thus be used by alternate steps of carrying out the acylation, followed by reactivationof the catalyst.

j .It is accordingly an object of the present invention to .provide an eflicient process for synthesizing acylated furans. Another object is to provide a process for catalytically acylating furan and its derivatives. A still further object is'to afford aprocess for catalytically acylating furan in a direct manner that can be easily carried out using a relativelyvinexpensive catalyst in small amounts. A very important object is to provide a catalytic process for acylatingfuran inthe presence. of a catalyst which can be easily reactivated and thus lend itself to use in a continuous. operation.

I These. and other objects which will be recognized by those skilled in the art are attained in accordance with the present invention wherein furan or its derivatives are acylate d by reaction with, organic carboxylic acid anhydrides in the presence of a porous absorptive silica-hydrous metallic oxide catalyst. H

; halogen, "alkyl,

action. v v 30 and about 150 C, have been'iound satisfactory for effecting "the acyilation. ,However,

50 'o. atmospheres fhave .beenfound satisfactory for The catalyst to be usedherein may be either a naturally occurring deposit or a synthetic gel composite of silica and one or more hydrous metallic oxides. Thus, naturally occurring silicaaluminaclays of the montmorillonite type which have been :activated have been ifound to be effective catalysts for promoting the acylation of furans. Typical of such products is the, material sold under the trade name of Super-Filtrol; Othring clays, synthetic silica-hydrous metallic oxide catalysts such as those extensively employed in the cracking of petroleum hydrocarbons may be used. These catalysts are synthetic .pcrousabsorptivecomposites of silica and a metallic oxiide and may be formed in various ways as, for-example, precipitating silica/ on the hydrous oxide,

or the hydrous oxide onsilica, or by combining a silica, gel with the "hydrous oxide, or by "preparing a silica-hydrous oxi'de 'gel. Gel composites 'suitable "for use as catalysts in the present inventionfinclude silica in combination with -zircorria,

alumina, titania, thoria, and the like. The synthetic or naturally occurring 'silica-hydrous 'metallic oxide catalysts are employedin the process dffthis invention usually in a .fine'ly divided form andin amounts between about 1 and about '25 per cent; based on the "weight o fthe reactant-s.

The 'acylating' agents to be used-herein are organic *carboxylic acid anhydrides; Included in I this category are compounds such as the ke'tenes having thebasicstructuraliorrmila v creased reaction but, from a practical standpoint, this is not a very great effect with reactions such as involved herein, which, go readily at normal pressures. The temperature to be employed will depend on the time of reaction and themature vof the acylafiing a'gent arsed. Ordinarily, a pressure sufficient-to maintain the reactants in the liquid phase is employed and this is more or less dependent upon the particular temperature involved. As a general rule, the higher the temperature, the higher the pressure and the lower the-reaction time that is needed. Ttis,.:of course, to be understood that these re- ...action variables aremore or less interdependent.

Under the conditions encountered in the process if this invention, however, the reaction period silica to L'hydrous metallic oxide arsed will, in general, accordingly be not -'l'essthan 3:1 and prefeiably between "about 4:1 "and about "20:1.

The catalystlwhen used should preferably .have a jairly small particle size." After continued use in the acylation process, the 'silica hydrous metallic ox'ide catalyst becomes. spent due to "the deposition of impurities on its surface "and may and which uponaddition of water, yield organic carboxylicacidsi Thes'ewacylating agentsgmayibe mohoor .polybas'ic organic acids which maybe either runsaturated orsaturated. Thus, represervitative acylating agents to be used in this -inacids, such as acetic ,arihydride, .piiopionici 'arihy- L dride,ke'tene,etc.; the 'arihydr ides of unsaturated fatty acids, such as crotonic anhydride; and the anhydrides of dibas'icr acids, such 'as ph'tha'lic .an-

hydride; These acylating agentsare given merely byway of examples and are not toibe construed *as'TlimitiIig, since other-carboxylic acid arihydrides which w'ill readily suggest themselves 'to derivatives, including .those having substituents' of aihigbly negativeicharacter, such as carbonyl,

*es'ter, nitro-andcyano vgroups, may likewise be acylated in the presence of silica-hydrous me'tallieoxide composites.

which the reaction is Tcar- V ried out may vary over a wide extent, the upper.

llim'it'bein'g dependent on the lbo'iling point of The temperature at the..rea'ctan'ts at the specific pressure ofthe re- Temperatures varying "between about generally it is preferable to employjtemperatures in the 'loweizrange of from about 0 'C. to about Pressures between about 1' and about 1'0 eiiecting the acylation reaction The effect of increased pressure, theoretically, is toward in-' itself, derivatives o'fifuran' ventiohinclude the'arihydrides-df saturated'iatty be reactivated by heating in .air at. an elevated temperature .suiii'dient to burn off the impurities and "hence. restore the catalyst to its original activity; The original catalyst .may accordingly be re-used a considerable number of times 'before it 'degenerat'es completely and must be dis carried. The a'cylaltion process described herein mayibe carried ovlt either in afbatch .or continuous operation. In the former instance, 'the furan is contacted with an organic carboxylic acid anhydride inthe presenceot a silica-hydrous metallic oxide catalyst and the reactants are heated tor -a time su'fiicien't to effect .acylation.

' The catalyst is then .removedl'from the reaction tion, the reactants "the catalyst and product mixture and said mixture is distilled "to yield theacylated furan. Inacon'tinuons opera- .are contacted with a bed of allowed "to remain .in contact with catalyst at a "temperature .and for .a time .suificient to efiect acylation. 'The reaction products are then removed .from the catalystbed and subjected to distillation. Unneacted "-furan isrecycled, together with ai zfireshreaction mix tune of-lthis fcompeundxand :an' acylating agent.

The .tollowing detailed (examples :are for the purpose .of illustrating modes (of reflecting 'tthe acylation :or tiinran :ainaccordance with'theprocess of this invention. It is to be clearly understood that "this invention is not to be construed as 7 limited to the specific acylat'ing agents used 'or the 'specific'corrditions set forth in the examples.

. (Example! h ti l-grams (cam-die) o'ffuran, 10v

' grams mole") oi 95 per "cent acetic anhydr'ide,

and 1 gram of Supe'rd iltrolclay was heated 'over a temperaturerange of from I! to 20 *0. for a period oT"3"- 72"hours. At the end-of this time, the reaction product mixture was cooled and the clayresidueremoved by filtration. '"Iheresulting solution was distilled under reduced pressure. yielding 8 grams of Z-acetyliuran.

Example 2 A mixture of 34 grams (0.5 mole) of furan, 107 grams (1 mole) of 95 per cent acetic anhydride, and 5 grams of Super-Filtrol clay was heated at a temperature of 39%? C. for a period of 3 hours. At the end of this time, the reaction product mixture was cooled, the catalyst removed by filtration, and the resulting solution distilled under reduced pressure to yield 13 grams of Z-acetylfuran.

Example 3 A mixture of 34 grams of furan (0.5 mole), 107 grams (1 mole) of 95 per cent acetic anhydride, and 5 grams of super-Filtrol clay was maintained at a temperature of C. for a period of 6 hours. At the end of this time, the clay residue was removed by filtration and the resulting solution distilled under reduced pressure, yielding 12 grams of 2-acetylfuran.

Example 4 Example 5 A mixture of 34 grams of furan (0.5 mole), 107 grams (1 mole) of 95 per cent acetic anhydride, and 10 grams of glauconite were heated at a temperature of 44-45 C. for a period of 3 hours. At the end of this time, the reaction mixture was cooled, the catalyst removed by filtration, and the resulting solution distilled under reduced pressure to yield 5 grams of 2-acetylfuran.

From the above examples, it will be seen that silica-hydrous metallic oxide composites are effective catalysts for the acylation of furan. Likewise, furan derivatives having one or more substituent groups attached to the furan ring may be acylated in accordance with this invention. The acylated furans as produced in accordance with the process described herein have found a variety of uses and may be employed as solvents, addition agents for petroleum fractions, plasticizers, resin intermediates, and intermediates for chemical synthesis. Long chain alkyl furyl ketones may be used as synthetic lubricants, dielectrics, waxes and extreme pressure additives for mineral oils.

We claim:

1. A process for acylating furan with acetic anhydride in the presence of between about 1 and about per cent by weight of a silicaalumina catalyst. I

2. A process for acylating furan comprising reacting the same with a fatty'acid anhydride in the presence of from about 1 to about 25 per cent by weight of a silica-alumina catalyst at a temperature between about 0 C. and about 50 C. for a period between about 1 and about 10 hours.

3. A process for acylating furan comprising reacting the same with acetic anhydride in the presence of from about 1 to about 25 per cent by weight of a silica-alumina catalyst at a temperature between about 0 C. and about 50 C. for a period between about 1 and about 10 hours.

4. A process for nuclear acylation of an acylatablc furan comprising reacting the same with an organic carboxylic acid anhydride in the presence of glauconite.

5. A process for nuclear acylation of an acylatable furan comprising reacting the same with an organic carboxylic acid anhydride in the presence of from about 1 to about 25 per cent by weight of a porous absorptive silica-alumina composite.

6. A process for acylating furan comprising reacting the same with-an organic carboxylic acid anhydride in the presence of a porous absorptive silica-alumina composite.

7. A process for acylating furan. comprising reacting the same with an organic carboxylic acid anhydride in the presence of glauconite.

8. A process for acylating furan comprising reacting the same with an organic carboxylic acid anhydride in the presence of a porous absorptive synthetic silica-alumina gel composite.

9. A process for acylating furan comprising reacting the same with an organic carboxylic acid anhydride in the presence of from about 1 to about 25 per cent by weight of a porous absorptive silica-alumina catalyst, the silica-alumina ratio of which is between about 3:1 and about 20:1.

10. A process for nuclear acylation of an acylatable furan, comprising reacting the same with an organic carboxylic acid anhydride in the presence of a porous absorptive silica-alumina clay.

11. A process for nuclear acylation of an acylatable furan, comprising reacting the same with an organic carboxylic acid anhydride in the presence of a porous absorptive silica-alumina composite.

12. A process for nuclear acylation of an acylatable furan, comprising reacting the same with an organic carboxylic acid anhydride in the presence of a porous absorptive synthetic silica-alu mina gel.

13. A process for nuclear acylation of an acylatable furan, comprising reacting the same with an organic carboxylic acid anhydride in the presence of a porous absorptive silica-alumina catalyst, the silica-alumina ratio of which is between about 3:1 and about 20:1.

14. A process for nuclear acylation of an acylatable furan, comprising reacting the same with a fatty acid anhydride in the presence of a porousa-bsorptive silica-alumina composite.

HOWARD D. HARTOUGH. ALVIN I. KOSAK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Hackmuth May 30, 1944 OTHER REFERENCES Number 

